1. Field of the Invention
The present invention relates to an integrated circuit device such as a microcomputer and, more particularly to an integrated circuit device which can be set to a stand-by mode.
2. Description of the Related Art
A large-scale integrated circuit such as a microcomputer has a stand-by mode in which its operation is temporarily suspended for the purpose of reducing electric power consumption. When the microcomputer is set to the stand-by mode, a microprocessor of the microcomputer stops execution of a program. The stand-by mode is canceled to enable the microprocessor to execute the program when a stand-by cancel signal is supplied to the microcomputer from a peripheral unit. In general, such a microcomputer uses a plurality of types of stand-by cancel signals, and the kind of the job to be performed by the microcomputer after the canceling of the stand-by mode is determined by the type of the stand-by canceling signal. A predetermined period of time, referred to as "transient period" is required for such a microcomputer before the job is commenced after receipt of the stand-by cancel signal. In order to cancel the stand-by mode, each of the stand-by cancel signals has to be maintained during this transient period.
As a consequence, each peripheral unit is required to have a complicated oscillation circuit capable of producing, as the stand-by cancel signal, a pulse signal having a duration equal to the transient period. In addition, each peripheral unit cannot perform another task during this transient period.